TOSHIBA VF-AS3 inverter RS485 communication function

TOSHIBA VF-AS3 inverter RS485 communication function

Basic Information and Security Standards for Documents

1. Scope of application and core purpose

Applicable equipment: Toshiba VF-AS3 series full specification frequency converter, covering 200V level (0.4-55kW) and 400V level (0.4-280kW, including IP55 protection type), supporting 2 independent RS485 communication interfaces (Connector1/Connector2).

Core purpose: To achieve three major functions through RS485 bus - remote control (run/stop, frequency setting, torque adjustment), parameter reading and writing (internal parameter configuration of frequency converter), and status monitoring (output frequency/current/voltage, fault code, terminal status), supporting master-slave synchronous control between frequency converters without relying on PLC or upper computer.

2. Safety and usage restrictions

Mandatory safety requirements:

It is prohibited to plug and unplug RS485 communication cables with power on, and it is forbidden to connect Ethernet signals to the RS485 interface, otherwise it may cause the communication module to burn out or the frequency converter to malfunction.

Communication timeout parameters (F803/F823) must be set to avoid device loss of control during communication interruption. After timeout, "continue operation", "trip immediately", or "trip after deceleration" can be set (default to continue operation).

The limit for writing EEPROM is 100000 times (for parameter storage media), and there is no limit for writing RAM. It is recommended to use the P command to write frequently modified parameters (such as frequency commands) to RAM, and avoid writing frequently to EEPROM for parameters that do not need to be stored.

Usage restrictions:

The length of communication cables should match the baud rate (recommended ≤ 100m at 19200bps and ≤ 50m at 38400bps), and repeaters should be added for long distances.

The same RS485 bus can connect up to 32 devices, and the frequency converter number (F802) must be unique (0-247) and must not be duplicated.

Hardware wiring and transmission specifications

1. Definition of communication interface pins

VF-AS3 is equipped with two RS485 interfaces (Connector1/Connector2), both of which are RJ45 interfaces. The pin functions are as follows (key pins are bolded):

(1) Connector1 (default 2-wire system, non switchable)

Pin number, signal name, function description, wiring requirements

1/2/6- Reserved pins must not be connected to any cables, otherwise communication signals may be short circuited

4 RXA+/TXA+non-polar transmission and reception data positive terminal is connected to bus A line (usually red), and all devices are interconnected through this pin

5 RXB -/TXB - Non polarized transmission and reception data negative terminal connected to bus B line (usually blue), this pin is interconnected for all devices

7 Power pins are prohibited from connection to avoid power conflicts and burning interfaces

All devices with SG signal ground are interconnected with SG pins, and ultimately grounded at a single point (ground resistance ≤ 4 Ω)

(2) Connector2 (supports 2-wire/4-wire system, [F829] parameter switching)

Pin number 2-wire system function ([F829]=0) 4-wire system function ([F829]=1) wiring requirements

1/2- Reserved pins suspended, wiring prohibited

3- TXA+(transmitting data positive end) is only used by the 4-wire master station and connected to the RXA slave station+

RXA+/TXA+(transmit/receive positive terminal) RXA+(receive data positive terminal) 2-wire system is the same as Connector1; 4-wire system connected to the main station TXA+

5 RXB -/TXB - (transmit/receive negative terminal) RXB - (receive data negative terminal) 2-wire system is the same as Connector1; 4-wire system connected to the main station TXB-

6-TXB - (transmitting data negative terminal) is only used by the 4-wire master station and connected to the RXB slave station-

7 Power pins are prohibited from connection

8 SG signal ground interconnected with all equipment SG, single point grounding

2. Wiring specifications and hardware configuration

(1) Cable requirements

Shielded twisted pair cables must be used, with a conductor cross-sectional area of ≥ 0.22mm ² (AWG24) and a characteristic impedance of 100-120 Ω (matching RS485 bus impedance). The shielding layer needs to be grounded at both ends (if cross device grounding is required, equipotential bonding wires should be used to avoid ground current).

The distance between communication cables and the main circuit cables of the frequency converter (3-phase power supply and motor wires) should be ≥ 20cm. Parallel wiring or sharing of the same cable tray is prohibited to reduce electromagnetic interference (EMI).

(2) Required resistor configuration (cannot be omitted)

The stable operation of RS485 bus requires two types of resistors, and all nodes must be configured with:

Terminal resistance: 120 Ω/1/2W, only connected between the A+/B - pins of devices at both ends of the bus (such as the leftmost and rightmost frequency converters), to suppress signal reflection and avoid data transmission distortion.

Up and down resistors: 510 Ω/1/2W, each device's A+pin is connected to a 510 Ω resistor to+5V (or the positive terminal of the power supply), and the B - pin is connected to a 510 Ω resistor to GND. The purpose is to enhance the bus driving capability and avoid communication packet loss when weak signals occur.